題目描述

   1↵    ↵     2↵    /↵   3↵

 1 vector<int> postorderTraversal(TreeNode* root) {
 2         vector<int> v;
 3         if(root == NULL)
 4             return
 
 v;
 5         stack<TreeNode*> s;
 6         TreeNode* cur = root;
 7         TreeNode* prev = NULL;
 8         while(cur||!s.empty())
 9         {
10             while(cur)
11             {
12                 s.push(cur);
13                 cur = cur->left;
14             }
15             TreeNode* top = s.top();
 
16             if(top->right == NULL||top->right == prev)
17             {
18                 v.push_back(top->val);
19                 prev = top;
20                 s.pop();
21             }
22             else
23             {
24                 cur = top->right;
25             }
26         }
 
27         return v;
28     }